1. Field of the Invention
The present invention relates to optical pickup apparatuses to be mounted on an optical disk apparatus and, in particular, to an optical pickup apparatus improved so that the collimator lens is not scratched.
2. Description of the Related Art
Conventional optical pickup apparatuses to be mounted on an optical disk apparatus have a structure in which a laser diode, a grating, a polarizing beam splitter or a half mirror, a raising mirror, and a light detector, etc., are installed on the lower surface (first surface) of a base chassis, while a collimator lens is installed in a hole in the base chassis above the raising mirror in such a manner as to be exposed at the upper surface (second surface) of the base chassis, and a support base for an objective lens actuator is fixed to the upper surface of the base chassis.
It will be appreciated that such optical pickup apparatuses should be assembled in such a manner as not to scratch the collimator lens or other optical components.
Meanwhile, there has been proposed an optical pickup apparatus in which the allowable displacement of an objective lens holder in the tracking direction is limited by erecting a pair of stopper walls on the upper surface of a base chassis and inserting the pair of stopper walls into through holes in a support base for an objective lens actuator when mounting the support base on the base chassis to arrange the pair of stopper walls on either side of the objective lens holder (refer to Japanese Patent Laid-Open Publication No. 2001-319342).
There has also been proposed an objective lens positioning mechanism in which an actuator base is positioned tiltably in all directions against an optical body by providing a spherical or conical convex portion on either one of the optical body and the actuator base and fitting the convex portion into a circular recessed portion or hole provided in the other one of the optical body and the actuator base (refer to Japanese Patent Laid-Open Publication No. Hei 8-161756).
However, in such conventional optical pickup apparatuses as mentioned above, since the collimator lens is exposed at the upper surface of the base chassis and the objective lens actuator is movable horizontally on the upper surface of the base chassis until positioned and fixed adhesively to the base chassis, the support base for the objective lens actuator may come into contact with the collimator lens that is exposed at the upper surface of the base chassis to scratch the collimator lens. Alternatively, even in optical pickup apparatuses assembled without scratching the collimator lens, there is a possibility that dust comes in through the clearance between the support base and the base chassis in the vicinity of the collimator lens to be deposited on the collimator lens over time, resulting in contaminating the collimator lens to degrade the performance for recording and/or reproduction.
These problems cannot be solved easily even by employing such a technique as disclosed in Japanese Patent Laid-Open Publication No. 2001-319342, which intends to limit the allowable displacement of the objective lens holder in the tracking direction by erecting a pair of stopper walls on the upper surface of the base chassis and not at all intend to prevent scratching the collimator lens, or cannot be solved even by employing such a technique as disclosed in Japanese Patent Laid-Open Publication No. Hei 8-161756, in which the actuator base is positioned tiltably in all directions against the optical body.